The present invention relates to spas or therapy pools and more particularly concerns an improved drain arrangement which will avoid entrapment of an object or person that may inadvertently block the drain.
The common spa or therapy pool designed for home use is much like a conventional swimming pool in that it includes a water containing shell, drain and inlet connections, and a recirculating water pump forcing water into the pool through the inlet connection and extracting water from the pool through the drain connection. One of the significant differences between the conventional swimming pool and the spa or therapy pool is the size of the water container. Whether such a spa is designed and built as an adjunct of the conventional swimming pool, to be operated together with the pool, or is designed and built to be operated as a totally independent unit, it is generally of a considerably smaller size and depth. Therefore, the person using the spa is normally positioned much closer to the spa drain than such person would be when using the conventional swimming pool. In the latter case the drain, which is generally located at the bottom of the deepest section of the pool, may be from 6 to 10 feet below the water surface. In the case of the spa, the drain, also positioned in the bottom at a lower point (which is often in the center of the spa tub or shell), may be only a few feet from the surface. Thus, in the use of the spa there is a considerably greater likelihood that the user will come into contact with the drain.
Such contact with the drain can be dangerous, painful or even fatal. A typical drain is 5 to 8 inches in diameter and thus it is possible that the body of a person, when positioned in close proximity to the drain, may be drawn down upon the surface of the drain cover to thus completely block the drain openings. If the drain is blocked, the person may be entrapped and drowned.
A commonly used recirculating spa pump of 11/2 to 2 horsepower can draw a vacuum as high as 22 to 26 inches of mercury. A vacuum of this magnitude, drawn upon a drain opening, even where such opening is as small as 5 inches, may exert sufficient suction forces to prevent a young person, or even some adults, from pulling free of the forces exerted by a drain that is completely blocked by the body or clothing of such person. If the person is able to pull free of the sucking drain, bruises or welts may result. In at least one case, a child has been drowned in a spa when his abodmen inadvertently covered and blocked the drain, whereby he was entrapped at the bottom of the spa and unable to break free.
Where a spa or therapy pool is provided with a skimmer having an intake just below the water surface and a connection to the pump suction line, such a skimmer when operating properly will operate to relieve dangerous suction at a blocked main drain. However, such skimmers are generally provided with valves to adjust relative flow of water through the skimmer and through the main drain, which valves are easily and often closed to completely stop the skimmer action. Further, the skimmer by its very nature incorporates a strainer or basket having relatively small openings and such basket is frequently plugged when overloaded with debris or floating objects such as balls or plastic toys and the like. Even where a skimmer is provided, its intake is below the water surface and thus it withdraws water from the pool at all times so that the skimmer valve is often closed to disable the skimmer when the spa is in use. Further, should the main water level drop below the level of the skimmer input, recirculation is disabled because the pump will suck air through the skimmer. Therefore, the skimmer is not and cannot be a true safety device and, in fact, has not been accepted or approved as such by government officials having regulatory authority over safety of spas and swimming pools.
Accordingly, it is an object of the present invention to provide a reliable safety device for spa drains that eliminates or minimizes the above-mentioned problems.